This invention relates to resistance welding electrodes and particularly to such electrodes having a universally movable head to conform to a non-normal workpiece surface.
In the practice of resistance welding it is often desirable to use a welding electrode having a swivel head to conform to workpiece surface areas which are not normal to the chief axis of the electrode. This feature is particularly important where it is desired to minimize marring of a workpiece surface area by electrode indentation. Further, in such applications, it is desired to use extraordinarily good cooling of the electrode and workpiece to prevent marring the workpiece and hindering the swivel action.
In the U.S. Pat. No. 4,140,891, to Lenox issued Feb. 20, 1979, a resistance welding electrode is shown which is formed of a hollow shank carrying current and cooling fluid and an electrode head connected to the shank by a flexible housing of insulating material. The housing forms a chamber to contain the cooling fluid supplied through the shank. The flexibility of the housing allows the head to rock relative to the shank and also to move axially away from the shank under the influence of the pressure of the cooling fluid. When welding pressure is applied through the electrode to a workpiece, the shank is forced against the head to provide firm electrical engagement between those elements. This electrode is a great improvement over other commercially available electrodes, such as those of the ball and socket variety, which do not properly handle large welding currents and which may tend to hang up in off center positions and thus dent the workpiece when brought into contact therewith. However, the Lenox electrode flexible housing has been difficult to manufacture and has demonstrated difficulty containing the cooling fluid at full operating pressures.